// 统一导出

const PI = 3.14; 

function sum([a, b, c, d = 80]) { 
    return a+b+c+d;
}

class Person{ 
    constructor(name, age) {
        this.name = name;
        this.age = age;
    }
    hello(params) {
        console.log('hello everyone')
    }
}

export{sum, Person, PI}